Broadband or Mid-Infrared Fiber Light Sources

• US 20090204110A1
• Filed: 02/05/2009
• Published: 08/13/2009
• Est. Priority Date: 11/18/2005
• Status: Active Grant

• Current Assignee: Omni Continuum LLC
• Original Assignee: Omni Sciences Incorporated
• Inventors: Islam, Mohammed N.
• Granted Patent: US 8,055,108 B2
• Time in Patent Office: Days
• US Class Current: 606/9
• CPC Class Codes: G01B 9/02091 Tomographic interferometers, e.g. based on optical coherence
• CPC Class Codes: G01J 2003/102 Plural sources
• CPC Class Codes: G01J 2003/423 Spectral arrangements using lasers, e.g. tunable
• CPC Class Codes: G01J 3/0218 using optical fibers
• CPC Class Codes: G01J 3/0245 using an optical amplifier of light, e.g. doped fiber
• CPC Class Codes: G01J 3/108 for measurement in the infrared range
• CPC Class Codes: G01J 3/42 Absorption spectrometry; Double beam spectrometry; Flicker spectrometry; Reflection spectrometry beam switching arrangements G01J3/08
• CPC Class Codes: G02B 6/29349 Michelson or Michelson/Gires-Tournois configuration, i.e. based on splitting and interferometrically combining relatively delayed signals at a single beamsplitter
• CPC Class Codes: G02F 1/3528 for producing a supercontinuum
• CPC Class Codes: G02F 1/365 in an optical waveguide structure G02F1/377, G02F1/395 take precedence
• CPC Class Codes: G02F 2202/32 Photonic crystals
• CPC Class Codes: H01S 2301/085 solitons
• CPC Class Codes: H01S 3/06725 Fibre characterized by a specific dispersion, e.g. for pulse shaping in soliton lasers or for dispersion compensating [DCF]
• CPC Class Codes: H01S 3/06754 Fibre amplifiers H01S3/06708 takes precedence
• CPC Class Codes: H01S 3/094007 Cladding pumping, i.e. pump light propagating in a clad surrounding the active core
• CPC Class Codes: H01S 3/094069 Multi-mode pumping
• CPC Class Codes: H01S 3/094076 Pulsed or modulated pumping H01S3/1024 takes precedence
• CPC Class Codes: H01S 3/1024 for pulse generation
• CPC Class Codes: H01S 3/302 in an optical fibre
• CPC Class Codes: H01S 5/0064 Anti-reflection components, e.g. optical isolators
• CPC Class Codes: H01S 5/0085 : for modulating the output, i.e. the laser beam is modulated outside the laser cavity
• CPC Class Codes: H01S 5/0092 : for nonlinear frequency conversion, e.g. second harmonic generation [SHG] or sum- or difference-frequency generation outside the laser cavity
• CPC Class Codes: H01S 5/1092 : Multi-wavelength lasing
• CPC Class Codes: H01S 5/146 : using a fiber as external cavity
• CPC Class Codes: H01S 5/4012 : Beam combining, e.g. by the use of fibres, gratings, polarisers, prisms

Abstract

A broadband light source includes one or more laser diodes that are capable of generating a pump signal having a wavelength shorter than 2.5 microns, a pulse width of at least 100 picoseconds and a pump optical spectral width. The light source also includes one or more optical amplifiers that are coupled to the pump signal and are capable of amplifying the pump signal to a peak power of at least 500 W. The light source further includes a first fiber that is coupled to the one or more optical amplifiers. The first fiber including an anomalous group-velocity dispersion regime and a modulational instability mechanism that operates to modulate the pump signal. In one particular embodiment, the pump signal wavelength resides in the anomalous group-velocity dispersion regime of the first fiber and where different intensities in the pump signal can cause relative motion between different parts of the modulated pump signal produced through modulational instability in the first fiber. The light source also including a nonlinear element that is coupled to the first fiber that is capable of broadening the pump optical spectral width to at least 100 nm through a nonlinear effect in the nonlinear element.

Claims

1. A method of generating broadband light comprising:

generating a pump signal comprising at least one wavelength shorter than 2.5 microns, a pulse width of at least 100 picoseconds, and a pump optical spectral width;

modulating at least a fraction of the pump signal using a modulational instability mechanism, wherein the modulation instability mechanism generates a plurality of pulses within the pulse width of the pump signal;

coupling at least some of the plurality of pulses into one or more optical fibers; and

broadening the pump optical spectral width of the pump signal to at least 100 nm using a nonlinear effect in the one or more optical fibers.

2. The method of claim 1, wherein at least a portion of the one or more fibers is selected from the group consisting of a high-nonlinearity fiber, a dispersion-compensating fiber, a ZBLAN fiber, a fluoride fiber, an extended band fluoride fiber, a tellurite fiber, a chalcogenide fiber, a photonic crystal fiber, a hollow core fiber filled with a nonlinear liquid, and a hollow core fiber filled with a nonlinear gas.

3. The method of claim 1, wherein at least a fraction of the broadened pump optical spectral width is adapted to emulate a black body radiation in an infrared counter-measures system.

4. The method of claim 1, wherein at least a fraction of the broadened pump optical spectral width is adapted for use in spectral fingerprinting, and wherein one or more chemical species are identified based at least in part on a property the one or more chemical species selected from the group consisting of absorption at a plurality of wavelengths and reflection at a plurality of wavelengths.

5. The method of claim 1, wherein at least a fraction of the broadened pump optical spectral width is coupled to a Michelson interferometer and adapted for inspection of a sample selected from the group consisting of biological tissue and semiconductor wafers.

6. The method of claim 1, wherein at least a fraction of the broadened pump optical spectral width is coupled to a lens system and adapted for cosmetic surgery, wherein unwanted parts of skin are substantially ablated without substantial collateral damage to skin tissue.

7. The method of claim 6, wherein the at least a fraction of the broadened pump optical spectral width is in a wavelength range between approximately 3.2 microns and 4 microns.

8. A light source comprising:

one or more laser diodes capable of generating a pump signal comprising at least one wavelength and a pulse width of at least 100 picoseconds;

one or more optical amplifiers coupled to the one or more laser diodes, the one or more optical amplifiers adapted to amplify the pump signal and generate an output signal comprising a first part and a second part;

a wavelength conversion element adapted to receive the first part of the output signal, the wavelength conversion element comprising a nonlinear element coupled to a nonlinear optical fiber; and

a super-continuum generation element adapted to receive the second part of the output signal, the super-continuum generation element comprising one or more fibers, at least one of the one or more fibers comprising an anomalous group-velocity dispersion regime and a modulational instability mechanism that modulates the at least one wavelength of the second part of the output signal in at least a portion of the at least one of the one or more fibers, wherein the at least one wavelength of the second part of the output signal resides in the anomalous group-velocity dispersion regime for at least a fraction of the at least one of the one or more fibers, and wherein the super-continuum generation element is capable of producing a substantially continuous spectrum over a bandwidth of at least 100 nm.

9. The light source of claim 8, wherein the nonlinear element is selected from the group consisting of a semiconductor waveguide, a nonlinear crystal material, and a periodically poled lithium niobate.

10. The light source of claim 8, wherein at least a portion of the nonlinear optical fiber is selected from the group consisting of a microstructure fiber and a photonic crystal fiber.

11. The light source of claim 8, wherein at least a portion of the one or more fibers is selected from the group consisting of a high-nonlinearity fiber, a dispersion-compensating fiber, a ZBLAN fiber, a fluoride fiber, an extended band fluoride fiber, a tellurite fiber, a chalcogenide fiber, a photonic crystal fiber, a hollow core fiber filled with a nonlinear liquid, and a hollow core fiber filled with a nonlinear gas.

12. An optical system comprising:

one or more laser diodes capable of generating one or more optical signals;

a fiber amplifier coupled to the one of more laser diodes, the fiber amplifier capable of receiving the one or more optical signals and generating a pump signal comprising at least one wavelength;

a wavelength shifter coupled to the fiber amplifier, the wavelength shifter adapted to wavelength shift the at least one wavelength of the pump signal to a shifted pump wavelength based at least in part on a Raman wavelength shifting mechanism and to transmit an output signal, wherein the shifted pump wavelength is in a wavelength range between approximately 1700 nm and 1900 nm; and

a lens system adapted to receive the output signal and adapted for use in surgery, wherein unwanted parts of skin are substantially ablated without substantial collateral damage to skin tissue.

13. The optical system of claim 12, wherein the wavelength shifter comprises a Raman oscillator that comprises a high nonlinearity fiber and a plurality of optical gratings.

14. The optical system of claim 12, wherein the fiber amplifier comprises a gain fiber and one or more optical gratings.

15. The optical system of claim 14, wherein the gain fiber is a cladding pumped fiber.

16. The optical system of claim 12, wherein the shifted pump wavelength is in a wavelength range between approximately 1710 nm and 1740 nm.

17. A light source comprising:

one or more laser diodes capable of generating a pump signal comprising at least one wavelength and a pulse width of at least 100 picoseconds;

one or more optical amplifiers adapted to receive the pump signal and adapted to amplify the pump signal;

a wavelength shifter comprising a nonlinear element coupled to the one of more optical amplifiers and capable of generating a wavelength shifted pump signal; and

a super-continuum generation element comprising one or more optical fibers and coupled to the wavelength shifter, at least one of the one or more fibers comprising an anomalous group-velocity dispersion regime and a modulational instability mechanism that modulates at least a portion of the wavelength shifted pump signal in at least a portion of the at least one of the one or more fibers, wherein at least a portion of the wavelength shifted pump signal resides in the anomalous group-velocity dispersion regime for at least a fraction of the at least one of the one or more fibers, and wherein the one or more fibers are capable of generating a super-continuum with a substantially continuous spectrum over at least 100 nm of bandwidth.

18. The light source of claim 17, wherein at least a fraction of the one of more optical fibers is a photonic crystal fiber or a micro-structure fiber.

19. The light source of claim 17, wherein the nonlinear element comprises a periodically-poled lithium niobate, and wherein at least a fraction of the one or more optical fibers comprises a photonic crystal fiber.

20. The light source of claim 17, wherein the light source is adapted for inspection of wafers by coupling the light source to a Michelson interferometer and a lens system with a spectral domain analysis of an output signal from the Michelson interferometer.